The present invention relates to a laminated fuel cell used for directly transforming chemical energy into electric energy and more particularly a laminated fuel cell capable of generating high output power.
In conventional inner manifold type laminated fuel cells as shown in FIG. 1, both surfaces of an electrolytic plate or tile a are made into intimate contact with an oxygen electrode b and a fuel electrode c and an oxidized gas (OG) is supplied to the side of the oxygen electrode b while a fuel gas (FG) is supplied to the side of the fuel electrode c, whereby one cell element is provided. A plurality of such cell elements are laminated through separators d and oxidized gas supply and dischage holes and fuel gas supply and discharge holes are formed through the peripheral portions of the electrolytic plates a and separators d. Ridges and valleys e are defined on both of the major surfaces of each separator d to form gas passages through which the gases flow. The cell elements thus laminated are clamped by a pair of upper and lower holders and clamping or locking bolts are tightened so that the separator d in each layer forces the electrodes b and c to be uniformly pressed against the electrolyric plate a, whereby a fuel cell stack S is provided. The stack S is disposed within a vertical vessel f which maintains a predetermined temperature (for instance, about 650.degree. C.) and a predetermined pressure.
In conventional external manifold type laminated fuel cells, a plurality of cell elements are laminated in the manner described above with reference to FIG. 1 and are surrounded by a manifold h having an oxidized gas supply pipe g and a discharge pipe (not shown) and a manifold j having a fuel gas supply pipe i and a discharge pipe (not shown) as shown in FIG. 3.
In the conventional laminated fuel cells of the types described above, the plate a, electrodes b and c and separator d in each cell element are made each in the form of a square or substantially square plate having a relatively small surface area from the viewpoint of the fabrication, temperature distributions of the oxidized and fuel gases and pressure loss. Because, in the case where oxidized and fuel gases flow in crossed manner, a square or substantially square cell element is suitable for attaining less pressure loss and better temperature distribution; the square configuration is advantageous in easiness of uniformly tightening the cell elements. Also in the case where the oxidized and fuel gases flow in one direction or opposite directions in parallel with each other, the square or substantially square cell element has been adopted.
In order to increase the output power of a laminated fuel cell, the whole area of the cell must be increased since the output power of each cell element per unit area has some upper limit. Increase of the whole area of the cell may be effected by increasing the area of each cell element or increasing the number of the laminated cell elements.
However, in the conventional fuel cells using square or substantially square cell elements, one cell element is 1.2 m.times.1.2 m at most from the viewpoint of pressure loss in the directions of gas flows as well as undesired increase in temperture due to generated heat of the cell and therefore the output power generated is of the order of 2 KW at most. Therefore, in order to obtain high output power, a great number of cell elements must be laminated. But, the lamination of a great number of cell elements will cause uneven conditions between the upper and lower cell elements since the lower cell elements are burdened by the upper cell elements themselves. Thus, the number of limited cell elements per cell stack is limited to be of the order of 300 to 600 layers.
The lamination of cell elements is limitative also from the viewpoint of fabrication and transportation and the upper limit of the output power available per laminated fuel cell stack is 1000 KW at most.
A large-scale power generating plant may be constructed by connecting a large number of laminated fuel cell stacks with each other. The smaller the output power of each stack is, the more the number of modules in the plant is increased so that the number of pipe lines is increased and the operation of the plant becomes much troublesome.
In view of the above, the primary object of the present invention is to provide a laminated fuel cell which can attain high output power without degrading the performance and reliability, which can be fabricated and transported advantageously and which can overcome the problem of the difficult plant operation due to the increased number of pipe lines.
The above and other objects, effects and features of the present invention will become more apparent from the following description of a preferred embodiment thereof taken in conjuntion with the accompanying drawings.